The present invention relates generally to GPS-based vehicle guidance systems and more particularly to a method for providing an ideal swath path based on predetermined and user-inputted parameters and for providing an integrated display for the operator of a vehicle. The method provides vehicle position information, and more specifically, the method indicates to a user the actual location of the vehicle in relation to the calculated swath path, regardless of the mode of operation.
Tractors and other off-road work vehicles in the agricultural, mining and construction industries have typically operated with manual steering by the operator. Recent changes in control systems and the development of satellite-based navigation (GPS) systems, including those incorporating differential correction systems, have allowed tractors or other vehicles to operate in semi-automatic or fully automatic steering modes. Combining satellite navigation and ground-based navigation input signals precisely identifying vehicle position and speed with sophisticated on-board vehicle electronic control systems allow the tractor or other vehicle to steer itself with a high degree of accuracy when traversing terrain. The result is that precision farming practices are transitioning from a luxury to a necessity, capable of improving efficiency and yield in common farming operations, such as tilling, seeding, fertilizing, spraying and harvesting.
To provide this control, the prior art teaches using satellite-positioning information by an on-board vehicle navigation control system to accurately determine and control a vehicle's position while operating in a field. The operator will typically enter the planned route of the tractor or vehicle, or let the control system determine the most efficient route. The control methods are well known in the art, and may involve multiple position transmitters or receivers, with various signals used to derive vehicle location, elevation, direction of travel (vehicle heading), attitude and speed.
The task of precision guidance of an agricultural vehicle involves not only accurately determining vehicle position in a field, but also defining an efficient array of paths to be followed by the vehicle that will, in conjunction with the swath of an associated implement, create an overall swath pattern that efficiently and effectively covers the crop area of a field or work area. The pattern must be located and oriented on the field or work area, and the physical characteristics and limitations of the vehicle and coupled implement must be identified and provided to the navigation system. Implement or header width, location of the implement or header with respect to the vehicle, and limitations on vehicle and associated implement movement, such as minimum turning radius, must also be considered. With this information it is possible to define a series of swath paths for the vehicle to travel in an attempt to cover all cultivatable portions of a field without unnecessary gaps or overlaps.
Calculating the series of paths needed to cover an area without substantial gaps or overlaps is relatively straightforward when straight paths can be used; however, not all fields can be covered in this manner. Many fields require the use of paths having a curvature that varies along at least some portion of its length, whether to follow irregularly shaped boundaries, avoid obstacles within the field, follow topographic contours of the ground, implement agronomic farming practices, or to contour the ground for irrigation. Such conditions preclude a complete reliance on geometrically predefined paths, such as straight lines or constant radius curves. In order to provide generally equally spaced swaths, the path of each adjacent swath must change slightly compared to the prior swath path as the vehicle moves generally transversely across the field (i.e., from one swath to the next) because the radius of each curved portion of the swath path varies slightly from the adjacent swath path.
Vehicle guidance systems must be able to store and retrieve swath path information as well as determine new adjacent swath paths from a baseline swath path or create new swath paths from defined starting and ending positions. The number of swath paths to be stored and/or determined increases as the size of the field increases. For swath paths that include variable curvature along their length, the number of positional data points necessary to fully define the swath path between starting and ending points is significantly increased compared to using only starting and ending position points to create straight-line paths. The systems must also quickly present swath path and control information to the operator in an easily understood and useful manner, which requires computational efficiency. As the vehicle operator positions the vehicle near the start of a swath path and prepares to engage the vehicle navigation system, the system must quickly determine if a swath path has been stored in system memory or can be calculated from a swath path stored in system memory and then direct the vehicle to the closest, presumably most appropriate path. If no swath paths are stored in the system memory, then the system must alert the operator and direct the recording of a new swath path or allow the operator to provide a stored swath path from another memory source (i.e., change the removable memory media to one having stored swath path information).
Satellite-based vehicle guidance systems may periodically experience signal drift. Vehicle position signal drift introduces differences between the actual vehicle position and the vehicle position sensed by the vehicle guidance system. In precision farming applications, even slight discrepancies can have significant impact on the swath pattern in a field. As a result, vehicle guidance systems must be able to compensate for signal drift, adjusting the vehicle position sensed by the guidance system to match actual vehicle and implement position in the field.
It would be a great advantage to provide a method for more clearly indicating to the operator what direction to steer to stay on the ideal swath path. It would also be a great advantage to include a method for determining this direction indication based on an ideal stored path, the positions of the vehicle, operator selectable parameters and other vehicle parameters. It would be even more of an advantage to provide these features for both automatic and manual operation of a vehicle. In addition, it would be an advantage to provide guidance to the operator of the vehicle when making end of row turns and when properly lining up the vehicle prior to engaging automatic operation and beginning a new swath path. It would also be an advantage to provide an integrated display that includes features such as speed monitors, fault indicators, work progress tracking, implement control and a guidance indicator. These and other advantages are provided by the method and vehicle guidance system described below.